This is the second stage in developing a logistic function for predicting acute ischemic heart disease (AIHD) in the Emergency Room (ER). We will test the validity, reproducibility, and utility of the function, CIPI - Coronary Incident Predictive Instrument. The study includes six hospitals representative of acute care hospitals and the diverse patient populations in New England. The utility of CIPI is examined in terms of improvement of CCU admission practices. CIPI was empirically derived from 174 variables collected on 854 "eligible" patients at Boston City Hospital. Patients with one of ten IMIR (Imminent Myocardial Infarction Rotterdam) complaints were interviewed, had ECGs, and cardiac enzymes in the ER and at 72 hour followup. This approach will be employed at the six hospitals in order to examine the classification capability of CIPI and the reproducibility of the coefficients. Hospitals will be paired: major teaching, affiliates and non-teaching. Interrupted time series data will be collected on one hospital from each pair: seven months baseline, six months with CIPI available, and five months with CIPI removed. Alternate months with/without CIPI data will be collected in the remaining three hospitals. This design allows us to explore differential learning effects.